Modified Circuit

Today, we're diving into modified circuits for differential amplifiers using BJTs. What do you think happens when we replace traditional components with a current mirror?

I think it helps balance the current better!

Exactly! Current mirrors help set the tail currents accurately, which is crucial for amplifier performance.

How does it affect the gain?

Good question! The gains—both differential and common mode—improve with active loads. Think of it as a way to increase efficiency.

Now, let’s summarize: using a current mirror maintains balance and enhances amplifier performance by improving gain.

To analyze our modified circuit, how do we approach small signal models?

We replace the transistors with their small signal parameters!

Exactly! We calculate the small signal parameters like 'r' and gain factors to understand their impacts.

And how do we find the differential mode gain?

Right! It's derived from the small signal model by observing voltage differences and the operational ratios, typically expressed as A' = gm × Ro.

Remember, small signal models are essential for understanding the linear operation range of amplifiers.

Now let’s focus on the active load configuration. What are your thoughts on its importance?

I remember it means we can mirror the current for better efficiency!

Great recall! It allows current values to remain precise, leading to voltage gain without additional resistances.

Are the active loads better than passive ones?

Correct! Active loads reduce losses and can provide higher impedance, enhancing overall circuit performance.

Let’s summarize this point: active loads improve efficiency, accuracy, and gain ratios of our circuits.

Now that we covered gains, how do modifications affect both common mode and differential gains?

I think the common mode gain gets decreased while the differential gain increases!

Exactly! When we use current mirrors, it helps in suppressing common mode signals more effectively.

So, does that mean the circuit rejects noise better too?

Absolutely! This also leads to improved Common Mode Rejection Ratio, making the circuit robust against noise.

Let’s take away today’s lesson: modifications through current mirrors enhance differential gains and suppress common mode noise.